1. Field of the Invention
This invention relates to the field of microactuators for disk drive suspensions. More particularly, this invention relates to the field of a disk drive suspension piezoelectric microactuator assembly having a comb structure and operating in the d33 mode, and a method of manufacturing and integrating such a microactuator motor assembly.
2. Description of Related Art
Dual stage actuated (DSA) suspensions for disk drives are known. DSA suspensions employ a standard voice coil motor (VCM) or similar primary actuator which moves the entire suspension arm, and in addition they employ a second actuator referred to as a microactuator located on the suspension arm itself. The microactuator moves only a portion of the suspension arm depending on the exact location of the microactuators. Most microactuators are piezoelectric devices made of lead zirconate titanate (PZT). Such a microactuator may be referred to simply as a “PZT” herein for simplicity without intending any limitation as to the particular piezoelectric material used.
A typical PZT device used as a suspension microactuator 2 is shown in FIG. 1. The piezoelectric element 8 is sandwiched between a top electrode 4 and a bottom electrode 6. The device is poled using top and bottom electrodes 4, 6. This poling, combined with subsequent activation of the device using those same electrodes, produces both d31 and d33 expansion/contraction, with the d31 mode of expansion/contraction being mechanically coupled to produce fine movements of the suspension head. The device thus operates in the d31 mode. Multilayer (vertically stacked) microactuators have been proposed before that operate in the d33 mode.
Typical electrical connections to such devices are seen, for example, in commonly owned U.S. Pat. No. 8,498,082 and copending and commonly owned U.S. patent application Ser. No. 14/045,773. Another electrical connection technique that was previously used by the assignee of the present invention, by which is not admitted as being “prior art” within the legal meaning of that term, is shown in FIGS. 1 and 2 of provisional patent application No. 61/940,812 from which priority is claimed.
When an actuating voltage is applied to the PZT, the PZT expands and contracts lengthwise in the d31 mode of the piezoelectric material, and that d31 expansion or contraction is harnessed to move the suspension head radially across the data disk for fine position of the head over the desired data track.
PZT microactuators of this type are complex to mechanically and electrically integrate into a suspension, requiring a challenging sequence of steps to terminate the PZT often from opposing sides and multiple applications of both conductive and structural adhesives that must be thermally cured. The thermal curing can negatively impact performance of the PZT if the cure temperature approaches the Curie temperature. In one process used by the assignee of the present invention the typical PZT attachment process required 52 separate process steps.
Thin film sputtered bending microactuators have also been proposed although such devices are complex to integrate into a suspension. U.S. Pat. No. 7,282,836 discloses a PZT device in which different length electrodes result in a bending action.